NEW YORK (Reuters Health) - Whether variant forms of a gene
called EGFR increase or decrease survival with colon cancer
depends on whether the patient is male or female, new study
findings indicate.

Gender-related differences in colon cancer are recognized,
including lower rates among women and gender-related response
to treatment, according to the article in the journal Cancer
Research. Expression of EGFR has been linked with a worse
prognosis, but up until now, it was assumed that variants of
the gene had a similar effect in men and women.

The research team at the Keck School of Medicine in Los
Angeles, headed by Dr. Heinz-Josef Lenz, studied two variant
forms of EGFR. One of the variants involved a change at a spot
called codon 497 and the other involved a change in an area
known as intron 1.

To examine the effects of the variants on survival, the
researchers analyzed DNA from 318 patients with advanced colon
cancer who had all received similar treatment.

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When all 177 men and 141 women were considered, the EGFR
variants did not influence survival. However, when men and
women were analyzed separately, the variants affected survival
differently.

Specifically, in men, the codon 497 variant decreased the
usual survival period from 13.7 to 10.3 months. In women,
however, the variant increased survival from 14.0 to 16.0
months.

The intron 1 variant also acted differently in men versus
women. For the same genetic change, survival rose by 10.3 to
13.1 months in men, while it fell from 17.6 to 14.1 months in
women.

As to mechanisms that might explain these differences,
Lenz's group believes that it may relate to how the EGFR
protein interacts with male and female hormone receptors in the
colon.

These findings suggest, Lenz said in a statement, that gene
variants "should be evaluated differently in women and men and
that treatment decisions may depend on gender and not only on
(genetic) or clinical findings."